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Rotax 912 cylinder running hot

in 912 / 914 Technical Questions 11 years ago

  • Re: Rotax 912 cylinder running hot

    by » 11 years ago

    I cleaned and replaced the o-rings and gaskets in the right carb. Didn't help the overheating problem. Cyl #3 CHT stills climbs to ~300F in about 10 minutes. Seems like the CHT is fluctuating between 280-300F. Could the coolant be not flowing and boiling. Oil temps climbs to ~280F. Left side cyl #2 CHT stays normal, around ~220F. Since the CHT are measuring the coolant temperature, and the coolant from both sides mix, should'nt The #2 CHT rise too? Maybe cyl #3 is getting insufficient oil flow. Suggestions? I ordered an EGT system but won't have it installed for a week or so.
      
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  • Re: Rotax 912 cylinder running hot

    by » 11 years ago

    Tony,

    Might be a bad probe. You might try switching probes to opposite cylinders and see if the overheating appears on a different cylinder. The probe doesn't actually contact the coolant and can be removed easily without draining the coolant.

    You might also try spraying some starter fluid around the carb, carb boot, and intake manifold with the engine idling. If it speeds up, you have an air leak which can cause you to run lean.

    Bill.
      
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  • Re: Rotax 912 cylinder running hot

    by » 11 years ago

    Hi Tony,

    The CHT probe measures the metal temp. There is no fluid contact. Pull it out. It is a dry hole. You can do as Bill suggest and swap probes and wires too to add to that test. Your 50-50 coolant is only good up to 270F. You should not be going over 248F with 50-50 (per Rotax). If it gets too close or over its max rated temp it will vaporize and you won't have any cooling.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Rotax 912 cylinder running hot

    by » 11 years ago

    Thanks for the good suggestions. I will switch probes tomorrow. Nice to know the probe has no liquid contact. I use Evans coolant. I think it boils at 375F.

    Tony
      
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  • Re: Rotax 912 cylinder running hot

    by » 11 years ago

    Evens has a good boil point at 375F, but using it carries about a 20F-30F temp penalty. I can't use it in mine or other Flight Design CT's. It tends to put us right over the max. 50-50 mix will run cooler.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report
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